The UN is not a legislative body ... let alone the security council is not a toy ...
The UN is not a legislative body. It is not a representative form of government, much less representative per capita, actual number of citizens or any other metrics.
It is an avenue, nothing more. That includes the security council.
Remember that the permanent members of the security council also provide most of the manpower. It is not a toy to be utilized as 150 nations, each with equal voting rights, see fit.
As an American, I do not want nations who don't understand the strict separation of powers between state and federal, let alone nations that do not have the US' strict "civilians always, and I mean always, order the miltiary" attitude, involving themselves with the US military. No military should ever tell a nation how to run a nation, and no world organization should ever tell a federal nation how to run itself any more than a federal authority over a state.
I know that's a foreign set of concepts outside the US, but it has worked wonders for protecting individual rights in the US over several centuries. It's too bad most nations don't have the free press like we do that exposes its own nation when it does not. I absolutely love the fact that we Americans disagree, continually, with ourselves. There's nothing more dangerous than when nearly all Americans agree on something.
Hell, wasn't Firefly a sci-fi show set on this theme? That unification is not the best idea, because ideals will vary and the only way to ensure they will be heard is for higher authorities to defer all authority not explicitly granted to its lower forms of government?